The present invention concerns the problem of sealingly feeding conduits through a bulkhead which separates two environments having different characteristics such as different pressure, temperature, humidity etc. For example, in pharmaceutical, biotechnological or food industries, validation and accountability of equipment are vital in view of strict standards applicable in these industries. Such equipment often comprises isolation chambers in which specific conditions, such as sterility, must be maintained during the manufacturing process or a part of it. Validation of such equipment involves introducing various electronic measuring devices to ensure that the equipment provides the required conditions. It is therefore necessary for the wires of the measuring devices to pass into the isolation chamber without letting any exchange of fluids or gases occur between the isolated area and the surrounding environment. For example, in a lyophilization process, products are placed on shelves within the isolation chamber of the lyophilizer. The products are initially frozen and then dried under vacuum while heat is transferred by thermal conduction from the shelves in to the product. Accurate temperature and pressure values must be maintained in the chamber in order to achieve high quality products. For validation of lyophilisation equipment, series of thermocouples are employed in a plurality of locations within the chamber to measure the temperature of the shelves and the insulated wires of the thermocouples pass through a bulkhead which separates the surrounding atmosphere and the chamber. It is vital to ensure that no air or moisture passes along the wires of the thermocouples into the lyophilization chamber during the validation process.
Many other processes, including but not limited to sterilisation processes, equally require validation of the internal condition in the isolation chamber using sensors connected by wire between the chamber and the exterior environment via a bulkhead connector. In each case, it is necessary to ensure that the passage of the wire through the bulkhead connector does not provide any means by which cross-contamination between the isolated and external environments may occur. Other examples of processes which may involve feeding conduits between two different environments include processes such as heating of products in dry heat ovens, autoclaving or, indeed, connecting a sterile area to a non-sterile area having equal or differential pressures between the areas; including connecting various vessels or pipes.
A known technique employed to sealingly feed insulated conductors through a bulkhead employs a bulkhead which connects two different environments e. g. an isolation chamber with the external atmosphere. The bulkhead has a plurality of pre-formed through bores in which separate insulated wires are received loosely. A curable sealant is then filled into the spaces between the bores and conductor jackets thereby providing a leak-proof seal between the two environments. Such a method is described, for example, in U.S. Pat. No. 5,170,017 (Stanevich et al). A similar method is used in U.S. Pat. No. 5,831,217 (Jarvis et al).
The disadvantage of using curable sealants is that the gaps between the bores and the conductors may not be filled uniformly and therefore leakage may still occur. Another disadvantage lies in the difficulty of disassembling the wires once the sealant has cured and the run has been completed. Furthermore forming curable seals is an expensive and time consuming process.
Another known method is described in U.S. Pat. No. 5,596,176 (Everitt) which uses a combination of a sealant and a rupturable sealing gland for feeding a bundle of cables through a bulkhead. The sealing gland is fitted in an opening in a bulkhead and has a receptacle defined by a rupturable wall made from resilient elastomeric material. A bundle of cables pierces through the rupturable wall so that the elasticity of the pierced wall holds the cables of the bundle together thereby minimizing the gaps between the individual wires. A sealing compound is then potted into the receptacle. The above mentioned disadvantages associated with fluid sealants apply equally in such a system. In addition, rupturable glands are not suitable for multiple use.
A further known method is described in U.S. Pat. No. 6,215,065 (Cox). The method uses a thermoplastic grommet having an aperture for receiving a cable or a bundle of cables. The grommet is placed across a bore of a split tubular boot. A split is formed radially in the boot from the wall of the bore to the outer surface of the boot. Fasteners are provided around the outer surface of the split boot so that when the fasteners are tightened the split of the boot closes together and the walls of the boot bore compress the grommet. The grommet clamps around the cable providing a mechanical seal for the cable. The disadvantage of this method is that the force applied radially from the walls of the cable aperture of the grommet to the cable jacket has an axial component which stretches the grommet axially along the cable jacket without control thus reducing the fit of the cable aperture against the cable jacket.
Yet another prior art method is described in EP 1 049 228 A1 (Cables Pirelly) wherein a sealing device is provided for the passage of a cable between two volumes at different pressures. The device comprises a gland having a plurality of axially spaced elastomeric annular packing members. The members are compressed axially in a box so that the members clamp radially inward against the cable jacket and outward against the box. Washers are provided between the members to prevent axial expansion of the members. However, the packing member closest to the high-pressure volume has a sleeve which surrounds the cable and extends from the packing member into the high-pressure volume. A disadvantageous feature is that no external force is applied to the part of the sleeve which projects outside the box so a leak can still occur between the sleeve and the cable jacket at the free end of the sleeve.